Partial Selector: These do not contain the top level window information i.e. you would need an attach browser/attach window for it(It will work as top level window). We use them when we have to perform operations on the same window i.e you do not switch the windows. e.g working on a single window of a notepad.
Full Selector: These contains all the elements including the top level window. These are used when you switch between windows. e.g working on Excel, notepad at the same time and you need to switch between them!
This link would give you an insight on SendWindowMessage & Simulate Type.
When it comes to simulate type, yes it types fast because it is the fastest method amaong the three. It does not types sometimes because, it’s accuracy is not 100%. (It’s about 60%)
TimeOutMs: You can set this to the time after which the activity would throw an exception, when a UiElement is not found.
So None is used when you do not want the target to be ready i.e it immediately moves to the next activity, it is used when you want the WF to be fast and you do not wish to identify the UiElement
Interactive waits for a part of UIElement, i.e when the page is loading and has not yet loaded completely and you want the workflow to continue as soon as it finds a part of the element then you use this method!
Complete is used when you want the WF to identify the element completely, i.e there are certain elements that appears only when a webpage is loaded completely, then you use this method!